The present invention relates to an optical module which is formed by integrating an optical element, optical waveguide, or the like.
An optical module is a transducer from electrical energy to light, or from light to electrical energy. An optical module is constituted in hybrid integrated form by an optical element, an optical waveguide, an electrical circuit, and the like. An optical module is used, for example, in an optical fiber communications system.
FIG. 3 shows schematically the disposition of an optical waveguide and optical element in a conventional optical module. This is disclosed in the journal Optical Technology Contact Vol. 36, No. 4 (1998). On a principal surface of a mounting substrate 40, a depression 42 is provided. In the depression 42 is mounted an optical element 44. On the principal surface of the mounting substrate 40 is fitted an optical waveguide 46. The end portion 48 of the optical waveguide 46 is positioned over the optical element 44. The end portion 48 forms a mirror. Light 50 emitted by the optical element 44 is reflected by the end portion 48, and enters the core 52 of the optical waveguide 46. The light 50 proceeds in the direction shown by an arrow within the core 52, and is transmitted through the optical fiber or the like.
However, this requires both alignment accuracy when mounting the optical element on the mounting substrate and alignment accuracy between the mounting substrate on which the optical element is mounted and the optical waveguide. In particular, for an optical module such as an optical fiber requiring positioning accuracy with an error of xc2x11 to xc2x15 xcexcm, there is also a requirement to reduce as far as possible the number of locations at which this alignment accuracy is required.
Further, electronic instruments are required to be more compact and lightweight, as a result of which, compactness, light weight, and low cost are requirements for optical modules.
This invention solves this problem. The objective of this invention is the provision of an optical module which can be made more compact and lightweight.
(1) An optical module of this invention comprises:
a mounting member having a principal surface; an interconnect formed on the mounting member; and an optical element mounted on the principal surface and electrically connected to the interconnect,
wherein the mounting member is an optical waveguide for guiding light emitted from the optical element or light admitted to the optical element.
In a conventional optical module, on a mounting member is mounted an optical waveguide separate from the mounting member. In contradistinction, this invention has the mounting member and optical waveguide as an integral member. The optical module can therefore be made thinner. As a result, the optical module can be made more compact and lightweight.
In a conventional optical module, there are three members involved in the positioning: the mounting member, the optical waveguide, and the optical element. On the other hand, in this invention there are two: the mounting member (optical waveguide) and the optical element. Therefore, in this invention, the optical element positioning is made easier, and the bonding accuracy can be improved.
A light-admitting aperture or light-emitting aperture of the optical element may be disposed opposing the principal surface. Such an optical element may be, for example, a surface-emission laser.
A light-reflecting member may be provided on the optical waveguide. Through the light-reflecting member, light can be transmitted between the optical element and the optical waveguide.
(2) An optical module of this invention comprises: an optical element for emitting or admitting light; and an optical waveguide having a principal surface, with the optical element mounted on the principal surface, for guiding light emitted from the optical element or light admitted to the optical element.
This aspect of the invention has the same effect as the aspect (1) of the invention.
The optical element and the optical waveguide may be fixed with an adhesive member having light transmitting characteristics interposed between the optical element and the optical waveguide in such a way that the position of emission or admission of light of the optical element opposes the optical waveguide, and be subjected to bare chip mounting.
Bare chip mounting allows more compact and lightweight design than with package mounting. In this aspect, since the optical element is subjected to bare chip mounting, the optical module can be made more compact and lightweight. The optical element and optical waveguide and are fixed by an adhesive member having light transmitting characteristics. By virtue of this, the optical element and the optical waveguide can be fixed and an optical path between the optical element and the optical waveguide can be assured.
The optical waveguide may have a modifying portion whereby the direction of progress of the light is changed; and the optical element may be positioned to overlie the modifying portion. By virtue of this, the direction of progress of the light can be efficiently changed.
The modifying portion is formed in the optical waveguide, and the optical element is directly mounted to the optical waveguide having the modifying portion. By virtue of this, the relative positioning (distance and the like) of the optical element and modifying portion can always be maintained constant, as a result of which there can be no loss of focus with respect to the modifying portion. On the other hand, in the prior art, the optical element is not mounted directly on the optical waveguide, and therefore the optical waveguide and optical element are disposed separated from each other. For this reason, when both are fixed with respect to other elements, there is a possibility of relative movement between the two. Therefore, even if the positioning operation is achieved, thereafter there is the possibility of a change in the positioning caused by various influences (heat, external pressure, and the like).
It should be noted that in the expression xe2x80x9cpositioned to overlie the modifying portion,xe2x80x9d the term xe2x80x9coverliexe2x80x9d indicates that when seen projected from the optical element or modifying portion, both are disposed in positions such that it appears that both coincide.
On the principal surface of the optical waveguide may be further mounted a semiconductor element in addition to the optical element, and the optical element and the semiconductor element may be integrally sealed with a resin.
If the optical element and semiconductor element are mounted on the principal surface of the optical waveguide, the interconnect connecting the two may be made shorted. The formation of the interconnect on the mounting substrate can be single layer, and the interconnect formation is made easier. If the optical element and semiconductor element are integrally sealed with a resin, the strength of the optical module can be improved. If the optical element and semiconductor element are hybrid, the degree of integration of the optical module can be improved. By the improvement of this degree of integration, the cost can be lowered.
The resin may have light blocking characteristics. If light impinges on the semiconductor element, faulty operation of the semiconductor element is possible. By sealing the semiconductor element with a resin having light blocking characteristics, faulty operation can be prevented.
The semiconductor element may have a function of driving the optical element.
Since the optical element and the semiconductor element driving or controlling the optical element are mounted on the principal surface of the optical waveguide, the optical module can be made a module of high added value. A higher degree of integration of the optical module and a lower cost can also be achieved.
A circuit may be laminated directly on the principal surface of the optical waveguide. If a circuit is laminated directly on the principal surface of the optical waveguide, the mounting of the semiconductor element is not required. Therefore, it is no longer necessary to consider the reliability of connection between different components. In respect of connections between integrated circuit elements, the connections can be eliminated, and by virtue of this, the interconnect impedance characteristics and noise characteristics can be improved, while the effect of delays can be held to a minimum. The degree of integration on the principal surface of the optical waveguide can be improved, and a high degree of integration of the optical module and low cost can be achieved.
(3) An optical module of the invention comprises: an optical element; and a mounting member which has a function of an optical waveguide for guiding light emitted from the optical element or light admitted to the optical element and is electrically connected to the optical element or a semiconductor element associated therewith.
This aspect of the invention has the same effect as the aspect (1) of the invention.
(4) An optical module of this invention comprises: a mounting member having a principal surface and a lateral surface; and an optical element mounted on the principal surface, wherein the mounting member has a function of an optical waveguide, and an optical input/output terminal for the optical waveguide is provided on the lateral surface of the mounting member.
This aspect of the invention has the same effect as the aspect (1) of the invention. It should be noted that an optical input/output terminal means a terminal at which light is input, or a terminal at which light is output, or a terminal at which light is input and/or output.
It should be noted that optical elements include both elements which emit light and elements which receive light. The mounting member may be in plate, film, or other form, as long as it allows the optical element to be mounted.